1. Technical Field
This disclosure relates to a low cost passive battery discharge device.
2. Description of the Related Art
Two main types of batteries include rechargeable batteries and primary, non-rechargeable batteries. Rechargeable batteries may need to be completely discharged for reconditioning, or for State-of-Charge synchronization purposes. For these applications, battery chargers may include active discharge circuits which monitor the rate of discharge. A stand alone battery discharge device is shown in U.S. Pat. No. 5,107,196, where a resistor and LED provide illumination until the battery has reached a desired discharge state.
Primary batteries often have a requirement to be fully discharged before disposal. Current discharge devices use a fixed resistor or active circuit connected across the battery terminals to discharge the battery. This approach requires the use of relatively expensive connector to mate with the battery, or complicated independent switch mechanisms, U.S. Pat. No. 5,651,821 provides a carousel where batteries rotate through while in contact with a discharge circuit. At the end of the rotation, batteries are ejected to make room for new ones. This system suffers from several drawbacks, because it requires the battery to be retained within the carousel for an indeterminate period of time, and there is no assurance that the ejected batteries are fully discharged. When discharging a single battery, the entire multi-battery carousel must be present, which may be unreasonable in field operations.
U.S. Pat. No. 7,190,147 discloses a circuit and a switch which is isolated from the battery terminals by an insulator. A tab extending outside the container is pulled to remove the insulator, thereby allowing the switch to complete the discharge circuit.
Therefore, a need exists for a low cost, passive battery discharge device which can be issued as a single unit, and remain with the battery indefinitely.